[VOL. 2 



220 ANNALS OP THE MISSOURI BOTANICAL GARDEN 



forded instructive and useful aids to the study of botany and 

 plant distribution in particular. 



These two tendencies in botanic garden arrangement hold 

 good at the present day, and gardens may be found adhering 

 to one or the other plan. Both systems have their merits, and 

 where possible both may be followed with due regard to local 

 conditions, but a slavish adherence to the one or to the other 

 tends to court disaster and produce confusion rather than 

 edification. 



There is much to be said for the older ideas of separating 

 "herbaceous plants" from "trees and shrubs," and for mak- 

 ing an independent arrangement of the two classes, mainly on 

 the ground of cultural requirements. 



The natural system in plant houses, again, is almost cer- 

 tainly doomed to failure, and an arrangement on geographical 

 or ecological lines must perforce be adopted. 



How instructive such an arrangement may be is shown by 

 an arrangement of plants from alpine regions or by a collec- 

 tion of xerophytes representative of some particular desert 

 area of the globe. 



Plant physiology affords another basis for plant arrange- 

 ment and perhaps is fruitful of greater educational value than 

 almost any other system. It has the further advantage that 

 it lends itself to adoption in the smaller garden where a com- 

 plete conspectus of the vegetable kingdom is an impossibility. 



In some botanic gardens on the Continent, particularly at 

 Berlin, and to a smaller extent at Geneva and elsewhere, the 

 flora of mountain regions is arranged with an attempt at 

 actual verisimilitude as to soil conditions and altitudinal dis- 

 tribution of the zones of vegetation. The idea is an excellent 

 one, but its realization is liable to be far from perfect since 

 the limiting factors of altitude and climate are absent and the 

 plants of the mountain tops, deprived of their natural restric- 

 tions, tend to usurp more than their proper share of avail- 

 able space. 



In whatever manner the main garden may be arranged, 

 there should always be special portions set apart for certain 

 well-marked plant types, such as alpine and rock plants, sue- 



